(1) Summary of the Invention
The present invention relates to a novel dextran having a slushy, applesauce-like appearance with a particulate, gel-like structure in crude form produced by Leuconostoc dextranicum. In particular the present invention relates to Leuconostoc dextranicum NRRL-B-18242 which produces the novel dextran.
(2) Prior Art
Dextrans are glucose polymers synthesized by several genera of bacteria including Streptococcus, Lactobacillus and Leuconostoc (Schwartz, R. D. and E. A. Bodie, Appl Environ Microbiol. 48:678-679 (1984); and Lawford, G. R., A. Kligerman and T. Williams, Biotechnol. Bioeng. 21:1121-1131 (1979)). Primarily extracellular dextransucrase enzymes synthesize dextrans with molecular weights of 2.times.10.sup.7 and higher (Schwartz, R. D. and E. A. Bodie, Appl. Environ. Microbiol. 48:678-679 (1984)). The dextrans are primarily alpha 1,6 linked, but may also have alpha 1,4, alpha 1,2, and alpha 1,3 linkages which result in branched polymers of varying water solubilities and other properties (Niinobe, M. and T. Kobayashi, Nippon Nogeikagaku Kaishi 46:81-88 (1972)). Dextrans are presently used in a variety of industries, however, uses in foods are non-existent.
One use of dextrans in the food industry involves gel-filtration to concentrate or recover proteins from liquid wastes such as whey and cereal waste streams (Jeanes, A., ACS Symp Ser 45 284-298 (1977)). The dextrans can be used for other non-food purposes such as seed coating as described in U.S. Pat. No. 2,764,843 to Peake.
Dextran synthesis has been widely studied in the genera Leuconostoc, particularly in L. mesenteroides (Lawford, G. R., A. Kligerman, and T Williams, Biotechnol. Bioeng. 21:1121-1131 (1979); Niinobe, M. and T. Kobayashi, Nippon Nogeikagaku Kaishi 46:81-88 (1972); and Preobrazhenskaya, M. E. and N. A. Danilova, Prikladnaya Biokhimiya i Microbiologiya 10:539-546 (1974)). Leuconostocs offered several advantages for study First, they are unable to metabolize either dextrans (they contain no dextranases) or sucrose (no invertases or sucrose phosphorylases) (Jeanes, A., ACS Symp. Ser. 45:284-298 (1977)). Also, many Leuconostoc strains are prolific producers of sucrose-inducible extracellular dextran sucrases and are, therefore, abundant producers of dextrans. Finally, they are able to metabolize fructose, which is the by-product of dextran synthesis, as an energy source.
Dextrans in aqueous solution are generally characterized as thick and relatively clear or translucent. Usually the upper limit of dextran produced is about fifty percent (50%) by weight based upon the sucrose. The failure to use dextrans in foods is believed to be because of the properties of the food (texture, thickness, mouth feel) are not significantly enhanced by the prior art dextrans.